Mapping of major river terraces and assessment of their characteristics in Upper Pindar River Basin, Uttarakhand: A geospatial approach

Abstract

In the present paper, an attempt has been made to trace out the major terraces and analyse their characteristics in the Upper Pindar valley of the Uttarakhand state. The study is based on digital elevation model (DEM), satellite data-based terrain characterisation with field and ground truth investigations. The results are derived from the data, which shows the preservation of river terraces along the trunk and tributary streams of the Pindar River. The terraces are formed because of the combined effect of local structural, geological, lithological, and tectonic control along with the climatic influence on landform development. Among the eight surveyed terraces, seven are cut and fill type and influenced by climate, tributaries, formed by both glacial and fluvio-glacial processes, whereas the rest terrace is developed because of tectonic uplift and creates a strath type. The terrace of Upthar and T3 of Langari has gone through the past tectonic events operated within this region. The analysis through cross-section profiles also exhibits the fact that the Upper Pindar basin has experienced a maximum of three stages of terrace development during different phases of the Holocene period and Late Pleistocene period. The alternative river aggradation, degradation, local landsliding, and a sudden increase in sediment flux caused by the monsoonal surge, tectonic uplift, and rapid incision in three separate times are the prime factors that are responsible for the generation of maximum three-tiered terrace landform in the study area. The sequence of terrace development reveals that the trunk of the Pindar River creates the highest number of terraces followed by the tributary rivers, which are generated in the later phase. The three phases of river aggradation in 33.5 ka, 17.5–13 ka, and 8–3.6 ka separated by a deep incision of different timescale are remarkable in this area, mainly around Langri and Khati, which creates the ordering of a maximum of three levels of terrace development. The results concluded that the dominance of local processes plays a vital role in the formation and characterization of river terraces in the Upper Pindar valley. The present study gives a detailed idea of the valley development and the result can also be used as an identification of suitable areas for human interactions with the environment.